Gas discharge display apparatus

ABSTRACT

A gas discharge display panel including reservoir cells for providing ionizable gas and a plurality of gas discharge display memory cells. Included are a plurality of addressing electrodes each having a plurality of apertures therethrough, the electrodes being arranged in superposed configuration so that the apertures align to form gas conductive channels extending from the reservoir cells to the display memory cells. The addressing electrodes are adapted for connection to sources of selectable electrical potential whereby gas discharge columns are extended from the reservoir cells through selected channels thereby igniting gas discharges in selected display memory cells.

United States Patent 91 Lustig et al. I

[111 3,781,587 [451 Dec 25, 1973 GAS DISCHARGE DISPLAY APPARATUS [75]Inventors: Claude D. Lustig, Lexington; Albert W. Baird, III,Burlington, both of Mass.

[73] Assignee: Sperry Rand Corporation, Great Neck, NY.

[22] Filed: Dec. 1, 1972 21 Appl. No.: 311,067

[52] US. Cl. 313/217, 313/220, 315/169 TV [51] Int. Cl. H01] 61/06 [58]Field of Search 313/217, 220

Primary Examiner-Roy Lake Assistant ExaminerDarwin R. HostetterAttorney-Howard P. Terry [57] ABSTRACT A gas discharge display panelincluding reservoir cells for providing ionizable gas and a plurality ofgas discharge display memory cells. lncluded are a plurality ofaddressing electrodes each having a plurality of apertures therethrough,the electrodes being arranged in superposed configuration so that theapertures align to form gas conductive channels extending from thereservoir cells to the display memory cells. The addressing electrodesare adapted for connection to sources of selectable electrical potentialwhereby gas dis charge columns are extended from the reservoir cellsthrough selected channels thereby igniting gas discharges in selecteddisplay memory cells.

15 Claims, 6 Drawing Figures obcde PATEHIED BECZ 5 E375 SHEEI b BF 5OOOOOO O0 O0 PATENIEDHEEZSIQH 3.731.587

SHEEISUFS W 8888 88888 II 88888 W 0 00000 00000 00000 00000 00000 0000000000 00000 00000 01 4 1 00000 00000 00000 00000 Ml 00000 Il00000|l00000 M00000 I 00000 00000 00000 00000 ULOOOOOIW 00000 H 00000,"!00000 L 00000 00000 00000 0000GT 00000 00000 00000 00000 H 8 88 8 88888888 l 00000 0 0 00 00000 00000 00000 M00000, M00000 00000 1'00000 0000000000 00000 00000 00000 m 00000,"! 00000 l| 00000, II 00000 W 0000000000 00000 00000- 0000 000 00000 00000 00000 00000 00000 00000 I 0000||00000 0000 |l 0 000 0 00000 0000 0 I 00000 00000 00000 00000 h 700000 00000 00000 00000 'I00000,l 00000 I' 0000 00000 I I 1L [1 0000000000! 88088 88088 00000 00000 0 0 00000 00000 00000 b00000 ,88888'8888888888 88888 [1 00000 00000 |\100000l\| 000000;

7 00000 00000 00000 00000 My 00000 H 000004 000003!" 00000 1 02 8 I 3 FG 3 SUSTAINING VOLTAGES FIG.l0.

FIG.4.

' l GAS DISCHARGE DISPLAY APPARATUS BACKGROUND OF THE INVENTION 1. Fieldof the Invention The present invention relates to gas discharge displaypanel apparatus particularly of the type suitable for the display ofsymbol and graphical information' 2. Description of the Prior Art Gasdischarge display panels are known in the prior art that utilizedot-matrix display formats for the visual presentation of information. Adot-matrix display panel is defined as apparatus incorporating a matrixof points which may be selectively lit to display patterns ofinformation. Such a dot-matrix display is described in US. Pat.application Ser. No. 90,538 filed Nov. 18, 1970 in the names of ClaudeD. Lustig and Albert W. Baird III entitled Digitally Addressable GasDischarge Display Apparatus" and assigned to the assignee of the presentinvention. Additional gas discharge dot-matrix display panelconfigurations were described in US. Pat. application Ser. No. 161,584filed July 12, 1971 in the name of Theodore H. Bonn, entitled GasDischarge Display Apparatus and US. Pat. application Ser. No. 244,01 1,filed Apr. 14, 1972 in the name of Claude D. Lustig,

'entitled D.C. Gas Discharge Display Apparatus with Pulse Train MemorySustaining Potential, both assigned to the assignee of presentinvention. Briefly, the device described in said Ser. No. 90,538comprises a reservoir of ionizable gas and a plurality of gas dischargedisplay memory cells. The device includes a plurality of addressingelectrodes each having a plurality of apertures therethrough.. Theaddressing electrodes are arranged in superposed configuration so thatthe apertures align to form gas-conductive channels extending from thereservoir to the display memory cells. The addressing electrodes areconnectible to sources of selectible electrical potential whereby gasdischarge plasma columns are extended from the reservoir throughselected channels igniting gas discharges in selected display memorycells.

Although such a display device is suitable for most purposes,limitations arise in applications requiring relatively large numbers ofdisplay points. This is so since the reservoir of ionized gas mustextend over the entire matrix of display points and thegas thereinmaintained uniformly ionized over the entire area of the reservoir. Withsuch a reservoir, 'one channel of the addressing anodes tends to drawcurrent before the other channels can do so and thus the single channelhas access-to a large number of electrons contained in the reservoir.Thus an excessively large current is extracted leaving little plasma forthe other cells. Difficulties are also encountered when endeavoring toignite simultaneously a plurality of cells. In addition, large areaionized gas reservoirs may be exceedingly difficult and hence expensiveto manufacture and may require prohibitively large quantities ofelectrical power.

With the display panel of said Ser. No. 90,538 when large numbers ofdisplay points are utilized, large numbers of super-posed and alignedaddressing electrodes are consequently required, further complicatingconstructional procedures and increasing manufacturing costs.Additionally, the binary addressing scheme of these panels are notparticularly commensurate with alphanumeric display requirementsutilizing, for example, a conventional X 7 matrix of dots for eachsymbol.

SUMMARY OF THE INVENTION The present invention overcomes thedisadvantages of the prior art discussed with respect to said Ser. No.90,538 while retaining the advantages thereof. The present inventioncomprises a gas discharge display having a plurality of gas dischargedisplay memory cells and reservoir means for providing ionizable gas.The display includes a plurality of addressing electrodes each having aplurality of apertures therethrough. The addressing electrodes arearranged in superposed configuration so that the apertures align to formgas conductive channels extending from the reservoir means to thedisplay memory cells. The addressing electrodes are adapted forconnection to sources of selectible electrical potential whereby gasdischarge plasma columns are extended from the reservoir means throughselected channels thereby igniting gas discharges in selected displaymemory cells.

The problems associated with a single channel extracting an excessivelylarge amount as discussed above with respect to said Ser. No. 90,538,are obviated by utilizing means for partitioning the reservoir into aplurality of essentially isolated cells.

The problems associated with the high cost and high power consumption ofa large area ionized gas reservoir are obviated by configuring thereservoir so that sub-sections of it may be selectivelyignited by meansof an X-Y selection arrangement.

The problems associated with requiring large numbers of addressinganodes discussed above with regard to said Ser. No. 90,538 are obviatedby utilizing control anodes with portions arranged commensurate with thedisplay of symbolic or graphic data such as alphanumeric charactersutilizing, for example, a S X 7 dot-matrix symbol block for eachcharacter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, comprised of FIGS. 1a, 1b and1c, is an exploded perspective view of a preferred embodiment of theinvention where FIG. 1a illustrates the reservoir means, FIG. 1billustrates the addressing electrode means, and FIG. 1c illustrates thedisplay memory cell I means;

FIG. 2' is an elevation view of one of the addressing anodes of FIG. lb;

FIG. 3 is an elevation view of one of the display memory electrodeplates of FIG. 1c illustrating a modification thereof; and

FIG. 4 is a chart illustrating how FIGS. la, lb and 1c combine to formFIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT thereof are comprised of anysuitable insulating material. A suitable choice of materials may, forexample, be nickel-iron alloy (51 percent nickel and 49 percent iron) ofa type in wide spread commercial usage in electron tube devices andsoda-lime glass, respectively. The coefficients of thermal expansion ofthese materials are substantially identical providing manufacturingadvantages well appreciated in the art.

The display panel illustrated in FIG. 1 is adapted to be filled, by anyconvenient method (not shown), with a suitable ionizable gas such as,for example, neon or a Penning mixture (99.5 percent neon and 0.5percent argon) or other suitable mixtures to which mercury vapor may ormay not be added.

Referring to FIG. 1a the reservoir 10 is comprised of a reservoir anodeplate 13, an electrically insulating plate 14, a reservoir cathode plate15, another electrically insulating plate 16, an electrically insulatingspacer plate 17 and a cover plate'20. An additional electricallyinsulating plate 21 is'included to electrically isolate the reservoir 10from the addressing electrodes of FIG. lb in a manner to be described.Each of the plates 13-16 and 21 has a matrix of apertures therethrougharranged in rows and columns. The matrix of apertures in each plate maybe comprised of a plurality of sub-matrices, for example 5 X 7sub-matrices of apertures, convenient for defining the symbols to bedisplayed.

Plates 13-17, 20 and 21 are assembled to form a reservoir adapted to befilled with an ionizable gas as previously described. The plates 13-15and 21 are superposed, i.e., stacked with respect to each other so thatthe respective matrices of apertures are in alignment, the correspondingapertures through the anode plate 13, the cathode plate 15 and theinterposed insulating plate 14 defining a plurality of gas dischargereservoir cells. The apertured insulating plates 14 and 16 provide meansfor isolating the gas discharge reservoir cells from each other thusproviding means for partitioning the reservoir into isolated gasdischarge reservoir cells. The electrically insulating spacer plate 17includes openings 22 and 23 each of which encompasses a plurality of thereservoir cells. The openings 22 and 23 provide weak coupling betweenthe reservoir cells in a manner and for reasons to be discussed. Theplate 17 also includes a member 24 for structural rigidity. It will beappreciated that the member 24 is not germain to the invention and mayoptionally be utilized as required.

A source of ionizing potential 25 is included for applying gas dischargeionizing potentials between the reservoir anodes 13 and thereservoir-cathodes thus ionizing the gas in the reservoir cells. Thesource may provide square voltage pulses for the purpose of ionizing thegas in the reservoir cells. Alternatively, to reduce the probability ofarc formation, the source 25 may provide voltage pulses containing astep where the voltage amplitude during the earlier part of the pulse ishigher than the amplitude in the later part of the pulse. Anotheralternative voltage waveform which may be utilized to reduce arcformation is where the source 25 provides a burst of short voltagepulses to ionize the gas in the reservoir cells with the amplitude ofthe pulses providing either a square envelope or an envelope containinga step as described above. These pulses may be conveniently synchronizedwith the pulses used to operate the memory display section 12 asdiscussed in said Ser. No. 244,01 1. Voltage waveforms of the typedescribed may be generated by the source 25 utilizing conventionalcircuitry well known in the art.

For convenience, the reservoir 10 may be configured in an X-Y selectionarrangement. Accordingly, the reservoir anode plate 13 is comprised ofsubstantially parallel electrically conductive strips 26 and 27electrically insulated from each other and the reservoir cathode plate15 is similarly comprised of substantially parallel electricallyconductive strips 30 and 31 electrically insulated from each other andoriented transversely with respect to the strips 26 and 27. The sourceof ionizing potential 25 selectively provides gas discharge ionizingpotentials between the anode strips 26 and 27 and the cathode strips 30and 31 by conventional switching means, not shown for simplicity.Accordingly, the gas discharge reservoir cells in the intersection. of aselected reservoir anode strip and a selected reservoir cathode stripmay be selectively ignited. For example, with gas discharge ionizingpotential applied between the strips 26 and 31, the gas dischargereservoir cells in the submatrices 32, 33, 34 and 35 are ignited thusproviding sources of plasma for the corresponding portions of thedisplay panel in a manner to be described.

Although each of the reservoir electrodeplates 13 and 15 is illustratedas comprising two parallel electrode strips, it will be appreciated thatin practice each plate will comprise larger numbers of strips, the anodestrips of the plate 13 being oriented orthogonally with respect to thecathode strips of the plate 15 thus dividing the reservoir 10 intogroups of independently ionizable reservoir cells. Alternatively, thereservoir electrode plates 13 and 15 may each be a unitary structurewhereby all of the reservoir cells will be ignited and extinguishedsubstantially simultaneously upon application and removal, respectively,of ionization potential from the source 25. 7

As previously mentioned, the electrically insulating apertured plate 21electrically isolates the reservoir 10 of FIG. la from the contiguouslystacked addressing electrodes of FIG. 1b.

Referring now to FIG. 1b, the stack of addressing electrodes 11 iscomprised of addressinganode plates 40, 41, 42 and 43 each of which hasa plurality of apertures therethrough forming a matrix configuration ina manner similar to that described with respect to the plates of FIG.1a. interposed between the addressing anode plates 40, 41, 42 and 43 areelectrically insulating plates 44, 45 and 56, respectively, each havinga matrix of apertures therethrough in a manner similar to that describedwith respect to the addressing anode plates 40-43.

The addressing anode plate 40 is comprised of substantially parallelelectrically conductive addressing strips 50, 51, 52 and 53. Each of thestrips -53 encompasses a plurality of rows of the matrix of apertures,for example 7 of the rows corresponding to the heights of the symboldefining 5 X 7 sub-matrices. The addressing strips 50 and 52 areelectrically connected to each other as are the strips 51 and 53 forreasons to be explained.

The addressing anode plate 41 is comprised of substantially parallelelectrically conductive addressing strips 54, 55, 56 and 57 orientedorthogonally with respect to the strips 50-53. Each of the strips 54-57encompasses a plurality of columns of the matrix of apertures, forexample five of the columns corresponding to the widths of the symboldefining 5 X 7 sub-matrices. The addressing strips 54 and 56 areelectrically connected to each other as are the strips 55 and 57 forreasons to be discussed.

The addressing anode plate 42 is comprised of a plurality ofelectrically conductive strips 60 substantially parallel to the strips50-53. Each of the strips 60 encompasses a row of the matrix ofapertures through the plate 42, thus defining the symbol to be displayedin a manner to be described. The strips 60 are arranged in groups ofseven strips each corresponding to the seven rows of the symbol defining5 X 7 sub-matrices. The strips 60 are interconnected in a to-and-froarrangement in a manner to be clarified hereinafter with respect to FIG.2.

The addressing anode plate 43 is comprised of a plurality ofelectrically conductive addressing strips 61 substantially parallel tothe strips 54-57. Each of the strips 61 encompasses a column of thematrix of apertures through the plate 43. The strips 61 are arranged ingroups of five strips each corresponding to the columns of the symboldefining 5 X 7 sub-matrices. The strips 61 are interconnected in ato-and-fro arrangement in a manner to beexplained with respect to FIG.2.

Referring now to FIG. 2 an elevation view of the plate 43 isillustrated. As previously described with respect to FIG. 1b, each ofthe strips 61 encompasses a row of the matrix of apertures through theplate 43. The strips 61 are interconnected in a to-and-tro pattern bymeans of interconnecting strips 62. The strips 61 and 62 areinterconnected in substantially the same plane to form fivenon-overlapping strips disposed in a to-and-fro manner in the plane ofthe addressing plate 43. It is appreciated that each of the fivecontinuous strips encompasses one column of each of the 5 X 7sub-matrices of the matrix of apertures through the plate 43. Forexample, the strip 61a encompasses the left-most column of thesub-matrices 63-66 and 73-76 and the right-most columns of thesub-matrices 67, 70-72, 77 and 80-82. In a similar manner, the strips61b-61e encompass the remaining columns, respectively, of the symboldefining 5 X 7 sub-matrices 63-67, 70-77 and 80-82.

Referring again to FIG. 112, it will be appreciated that the addressingstrips 60 of the addressing anode plate 42 are arranged in a to-and-froconfiguration in a manner similar to that illustrated in FIG. 2 exceptthat the rows of the sub-matrices are encompassed by 7 continuouselectrically conductive strips.

The addressing strips 50-57, 60 and 61 are connected to addressingcircuits 83 which comprise conventional circuits for selectivelyapplying either a positive or a negative potential to each of theaddressing strips in a manner and for reasons to be discussed.

The plurality of gas discharge display memory cells 12 of the displaypanel are illustrated in FIG. 1c and are I stacked contiguously withrespect to the addressing electrodes of FIG. lb. The display memorycells of the present invention are similar to those disclosed in saidSer. No. 90,538 and said Ser. No. 244,011.

Referring now to FIG. 10, the gas discharge display memory cells 12 arecomprised of a display memory anode plate 84 and a display memory'cathode plate 85. An electrically insulating plate 86 is interposedbetween the plates 84 and 85. A transparent face plate 87, through whicha display pattern may be viewed, is also included in the display memorycell section 12. Two electrically insulating plates 90 and 91 aredisposed between the cathode plate and the transparent face plate 87 toinhibit sputtering of material from the cathode plate 85 to the faceplate 87 which sputtered material would tend to obscure the display.Additionally, an electrically insulating plate 92 is disposed betweenthe display memory anode plate 84 and thc addressing anode plate 43(FIG. 1b).

Each of the plates 84-86 and -92 has a matrix of apertures therethroughidentical to those through the plates described with respect to FIGS. 1aand lb. The plates of FIG. 1c are disposed adjacent one another insuperposed, i.e., stacked, arrangement with the matricesof aperturesthrough the respective plates aligned to form the plurality of gasdischarge display memory cells 12 in the manner disclosed in said Ser.No. 90,538 and said Ser. No. 244,01 1. I

A suitable source 93 of gas discharge sustaining potential is connectedacross the anode plate 84 and the cathode plate 85 to providegasvdischarge sustaining potential thereto in the manner described insaid Ser. No. 90,538 or said Ser. No. 244,0l l.

It will be appreciated that the plates of FIG. lb are superposed, i.e.,stacked,lwith respect to each other so that the respective matrices ofapertures align to form a plurality of gas conductive channels extendingrespectively fromm the reservoir cells 10 of FIG. la to the plurality ofgas discharge memory display cells 12 of FIG. 10. Furthermore, all ofthe plates of FIG. 1 are contiguously superposed and sealed at the edgesthereof by any convenient means (not shown) to form a gas tightstructure. Alternatively, the plate members forming the display panelmay be mounted inside a gas tight envelope (not shown) with electricalconnections made through gastight seals in the envelope.

The operating principles of the display panel illustrated in FIG. 1 aresimilar to those discussed in said Ser. No. 90,538 and said Ser. No.244,011 and will be briefly explained herein for completeness. The gascontained in the reservoir cells 10 at the intersection of two of thereservoir electrode strips 26, 27, 30 and 31 is ionized by the source ofpotential 25 causing a glow discharge at the reservoir cathodeplate 15at the cells thus energized. The gas discharge sustaining potential isapplied across the display memory cells 12 by the source 93. By suitableapplication by the addressing circuits 83 of positive and negativepotentials selectively to the addressing strips of the addressing anodes40-43, gas discharge plasma columns are extended therethrough inselected channels to emerge from the selected apertures in theaddressing anode plate 43. The columns may be further extended byapplication of a positive potential to the display anode 84. Particlesfrom the excited gas discharge plasma columns enter the associated onesof the display memory cells 12 partially ionizing the gas therein andcausing ignition thereof by the voltage applied by the source 93. Thesource 93 maintains the discharges in' the selected memory cells afterthe discharge columns have been extinguished by removing the addressingpotentials. The displayed pattern of information in the memory cells 12may be erased by a momentary reduction or removal of the sustainingpotential from the source 93.

The detailed operation of the display panel of FIG. I will now beexplained in terms of displaying a symbol in the sub-matrix 77 of thedisplay memory cells 12 of FIG. 10. The source 93 of FIG. 10 providesthe sustaining potential to the plurality of gas discharge displaymemory cells 12. The source 25 of FIG. 1a provides gas dischargeionizing potential across the reservoir electrode strips 26 and 31 thusigniting the reservoir cells of the sub-matrices 32-35. The addressingcircuits 83 are activated to provide positive potentials to the addressing strips 50, 52, 54 and 56 of the addressing anode plates 40 and41, the remaining strips of these plates having negative potentialsapplied thereto. Under these conditions, gas discharge plasma columnsare extended through the sub-matrices of apertures in theaddressi'ng'strip 50 aligned with the sub-matrices 32 and 34 of thereservoir and are inhibited from passage through the apertures of ,theaddressing strip 51. Since the reservoir cells corresponding to theaddressing strips 52 and 53 are not lit, plasma columns are not extendedtherethrough. Of the discharge columns passing through the strip 50,only those incident upon the strip 54 of the plate 41 are transmittedtherethrough. Those columns incident upon the strip 55 are inhibitedfrom further passage. Thus, it is appreciated that by the application ofthe addressing potentials described above, gas discharge columns areextended through the apertures of the 5 X 7 symbol defining sub-matrix77, the strips of the plate 40 defining the height of the submatrix andthe strips of the plate 41 defining the width thereof.

With the symbol defining sub-matrix 77 selected by the addressingelectrode plates 40 and 41, gas discharge plasma columns are incidentupon the apertures of this sub-matrix of the plate 42. Addressingpotentials are applied to the addressing strips 60 and 61 of the plates42 and 43, respectively, by the addressing circuits 83 to extend theplasma columns through the plates 42 and 43 to define the symbols. Anaddressing potential is applied to the display anode 84 to extend theplasma columns from the plate 43 to the plate 84, to ignite the selecteddisplay memory cells 12 in the manner previously described. Onceignited, a pattern of lit cells will be maintained energized by thesustaining potential from the source 93 until erased by a momentaryreduction or removal of this potential. Addressing potentials may beapplied to the addressing strips 60 and 61 so as to simultaneouslyignite a plurality of the memory cells of a sub-matrix or the potentialsmay be applied to ignite a single cell. In this manner, the segmentscomprising alphanumeric characters or graphical display elements may besequentially'energized to form the symbols. For example, if it isdesired to simultaneously ignite a column of apertures of the sub-matrix77, positive addressing potentials are applied to all of the addressingstrips 60 and to the one addressing strip 61 associated with the columnof apertures to be ignited. Similarly, if it is desired tosimultaneously ignite a row of the apertures of the sub-matrix 77, apositive potential is applied to all of the addressing strips 61 and tothe one addressing strip 60 associated with the desired row. When it isdesired to simultaneously ignite selected cells in a column of thesubmatrix 77, positive potential is applied to the addressing strip 61associated with that column and to selected addressing strips 60associated with the selected apertures in the column that are to beignited. When a single display memory cell is to be lit, the selectedaddressing strips 60 and 61, at the intersection thereof, have positivepotential applied thereto to light the cell.

Thus, it is appreciated that by appropriate application of potentials tothe strips and 61, a wide variety of alphanumeric characters andgraphical symbols may be displayed and stored in the sub-matrix 77 ofthe plurality of gas discharge display memory cells 12. in a similarmanner other sub-matrices of the display may be selected for theformation and storage ofsymbols by appropriate application of potentialsto the addressing anode plates 40 and 41.

The amplitudes of the positive potentials applied by the addressingcircuits 83 to the respective addressing anodes 4043 and the displaymemory anode 84 are selected in increasing fashion to correspond to theincreasing distances of the respective anodes from the reservoir 10 inaccordance with the well known gas discharge laws. The voltages mustalso be selected to preclude' gas discharge breakdown between any of theelectrodes 13 and 40-43 in the manner described in said Ser. No. 90,538.Breakdown must further be prevented between the display memory anode 84and any of the electrodes 13, 15 and 40-43. This may be accomplished inthe manner described in said Ser. No. 90,538. The potentials provided bythe addressing circuits 83 may be narrow pulses having durationssufficient to ignite the display memory cells 12, which once ignited areso maintained by the source 93.

Since no series resistors are utilized in the circuits of the displaymemory cells 12, voltage drops do not occur when a large number of cellsare ignited, thus preventing faulty cell ignition prevalent in devicesrequiring these resistors.

It will be appreciated from the foregoing that when it isdesired tosimultaneously ignite a plurality of display memory cells 12, the plasmacurrent drawn from the associated reservoir cells 10 will dividesubstantially equally amongst the associated channels because of theisolation between reservoir cells provided by the apertured reservoirplates 14 and 16. Thus, the problem associated with the display panel ofsaid Ser. No. 90,538 as discussed above where one of the channels drawsmuch of the available current before the other channels can do so, isobviated in the present invention. Since the statistical time lag forbreakdown in the individual reservoir cells could be large and diverse,suitable interaction between the reservoir cells is provided by thereservoir spacer plate 17 providing weak coupling between the cells. Thecoupling between the cells is weak since the thickness of the spacerplate 17 is selected to be of a small value. In this way, some ionizedparticles can diffuse amongst the reservoir cells to provide prompt anduniform ionization of the gas in the cells but prevent large plasmacurrents from being drawn between cells. It is believed that a suitablevalue for the thickness of the spacer plate 17 is somewhat less than thewidth of the plasma sheath that surrounds the reservoir cathode 15.Additionally, it is believed that should the number of addressing anodeplates be increased, the thickness of the apertured plate 16 should beincreased.

In one embodiment of the display panel of the present invention, thefollowing parameters were found to be suitable in a 32 X 32 arrayoperating on the principles described above. The cells of the panel wereon a center to center spacing of 0.03l inch. The thicknesses of theplates 14, 16 and 17 were 0.006 inch. Satisfactory performance wasobtained with aperture diameters in the range of 0.010 to 0.014 inch forthe reservoir electrode plates 13 and 15. Since the reservoir currentrequired for operation is proportional to the thickness of the reservoircathode plate 15, satisfactory'performance was obtained with a cathodethickness of 0.0025 inch and it is believed that smaller thicknessesshould be possible. The thickness of the display memory cathode plate 85was also 0.0025 inch. The thicknesses of the addressing electrode plates40-43 were 0.005 inch and the apertures therethrough were 0.010 inch indiameter. The thicknesses of the insulating plates 21 and 44-46 were0.006 inch with 0.018 diameter apertures therethrough. The paneloperated with a pressure of 100 torr of neon gas.

It will be appreciated that when the reservoir 10 includes X-Yaddressing, an economical mode of opera tion is obtained. For example,the reservoir cathode may be divided into N strips and the reservoiranode 1'3 into M strips orthogonal to the cathode strips. Thus, by meansof M+M circuits any one of the N M sections in the reservoir may beignited. The advantages of this mode of operation are:

l. The total number of reservoir cells which have to be ignitedsimultaneously in the reservoir is relatively small so that some form ofcurrent limitation may be incorporated to prevent arc formation;

2. The net power dissipation in the reservoir 10 is reduced resulting inreduced heating and lower circuit costs; and

3. The X-Y partitioning may result in fewer addressing anode plates inembodiments of the invention.

The reservoir 10 is constructed such that the individual reservoir cellsthereof perform independently when a plurality of channels areactivated.The current therefore divides approximately equally amongst thechannels. For optimum addressing of the channels, almost completeisolation is utilized between the reservoir cells. The plate 17,however, may be included to provide' at most weak coupling amonst thereservoir cells to achieve prompt and uniform ionization of the gas inthe cells. Additionally, the openings such as 22 and 23 in the plate 17may conveniently be utilized as an evacuation space during the pumpingoperations in the manufacturing procedures for the panel.

It will be appreciated that when larger numbers of X-Y reservoirelectrode strips than those illustrated are utilized, additionalsub-matrix defining addressing strips must be utilized in the addressingplates 40 and 41 with strips associated with corresponding locationswith respect to the reservoir intersections commonly connected. Thelengths of the row and column addressing strips in'the addressing plates42 and 43 would be lengthened to accommodate the additional submatricesof apertures. It will furthermore be appreciated that should thereservoir 10 be constructed without X-Y addressing where all of thereservoir cells are simultaneously ignited, the interconnections amongstthe strips of the addressing plates 40 and 41 would not be utilized andeach strip would be separately addressed to individually actuate theindividual 5 X 7 symbol defining sub-matrices. Alternatively, if thereservoir 10 is constructed with X- Y addressing such that eachreservoir intersection encompasses one 5 X 7 symbol defining sub-matrix,the addressing plates 40 and 41 would not be required.

Although the present invention has been described in terms of an X-Yaddressed reservoir, other reservoir configurations may also be utilizedsuch as a scanning reservoir of the type described in said Ser. No.l6l,584. With a scanning reservoir where the reservoir sections comprisea symbol defining sub-matrices, only the row and column definingaddressing plates 42 and 43 would be required.

The reservoir 10 has been described hereinabove with the anode plate 13and the cathode plate 15 positioned as illustrated in FIG. la. It isbelieved that the positions of these plates may be interposed withrespect to each other with a possible repositioning of the spacer plate17.

From the foregoing, it will be appreciated that when utilizing thearrangement of the addressing strips of the plates 4043, feweraddressing plates are generally required than when utilizing theaddressing plate arrangement of said Ser. No. 90,538. Further advantagesaccrue to the to-and-fro interconnection arrangement described above ofinterconnecting many non-adjacent addressing anode strips in one plane.The to-and-fro arrangement eliminates the need for the conventionalinterconnection schemes utilizing through plate connectors. A to-and-frointerconnected addressing plate is readily constructed by initiallyhaving the ends of the continuous strips connected together. and cuttingoff the connecting portions following assembly of the panel in themanner of the conventional lead-frame technique. Furthermore, althoughthe to-and-fro inter connecting arrangement has only been illustratedwith regard to the plates 42 and 43, this construction may also beadvantageously utilized with regard to the plates 40 and 41. Althoughthe to-and-fro interconnection arrangement provides the advantagesdiscussed, the strips of the addressing plates 40-43 may be fabricatedand interconnected by more conventional means such as utilizing silkscreening with through plate connectors in constructing a display panelincorporating aspects of the invention.

The addressing electrode plates 40-43 have been described in terms ofthe relative positions illustrated in FIG. 1b. lt will be appreciatedthat these plates may have other positions relative to each other toachieve the same effect. Although the display panel of the presentinvention has been described in terms of electrically conductive platesand electrically insulating plates interleaved with respect to eachother, it is understood that the panel may alsobe constructed bydepositing the illustrated electrode strips on insulating substrates.

As previously described, the addressing electrode plates 40-43 areparticularly suited to the display of symbol information such as that ofthe alphanumeric type. The term symbol as used herein is also meant toinclude graphical display elements which combine to form a graphicaldisplay.

The present display panel has been described herein in terms of thereservoir 10 as illustrated in FIG. 1a and the addressing electrodeplates 11 as illustrated in FIG. 1b. It will be appreciated thatalternatively, the addressing plates 11 may be utilized with reservoirsof the type described in said Ser. No. 161,5 84 and the reservoir 10 maybe utilized with addressing plate arrangements of the type illustratedin said Ser. No. 90,538 or .said Ser. No. 161,584. It will further beappreciated that although the present display panel was described interms of the display memory cells 12 of FIG. 10, the display memory cellarrangements of said Ser. No. 90,538 and said Ser. No. 161,584 may alsobe utilized. However, with the arrangement of FIG. 10 of the presentapplication, the cathode plate 85 at which the glow discharge occurs iscloser to the viewing plate 87 than the anode plate 84 which positionsthe displayed information closer to the viewer than with the conversearrangement to provide an efficacious display.

It is often a requirement in display panels of the type described hereinto provide an indicium indicating which symbol defining submatrix isactive for the entry of a character. This is particularly desirable ininstallations where characters may be entered into the panel by means ofa manually operated keyboard. Such indicia may be conveniently providedby the arrangement of FIG. 3.

Referring now to FIG. 3, an elevation view of one of the display memoryelectrode plates of FIG. 1c, including a modification thereof to providesuch indicia, is illustrated. It is appreciated that this modificationcan be effected with either the memory cathode plate 85 or the memoryanode plate 84 of FIG. 1b. It is believed that it is simpler to modifythe cathode plate 85. The modified cathode plate 85 comprises twoportions 100 and 101 electrically insulated from each other and adaptedfor connection independently to sources of gas discharge sustainingpotential provided by the voltage source 102. The portion 100 of theplate 85 contains the plurality of 5 X 7 symbol defining sub-matricespreviously discussed and the portion 101 Of the plate 85 includes theactive sub-matrix indicia. In a preferred embodiment of the invention,these indicia may take the form of rows of display memory cells disposedbeneath the sub-matrices respectively. Such indicia may be considered asa cursor for indicating a particular sub-matrix.

In operation, the voltage source 102 provides sustaining potentialindependently to the portions 100 and 101 of the plate 85 with respectto the plate 84. A particular group of cursor cells may selectively beignited in the manner hereinabove described. When it is desired tochange the position of the cursor cells, the sustaining potential may bereduced or removed from the portion 101 erasing the lit cursor cells andaddressing potentials applied as previously described, to ignite cursorcells in another location on the portion 101. Thus it is appreciatedthat the cursor cells may be extinguished and ignited without disturbingthe symbols stored at the sub-matrices of the portion 100. It is alsoappreciated that in order to accommodate a cursor configuration asillustrated in FIG. 3, additional apertures (not shown) would berequired through the remaining plates of the display panel correspondingto the apertures of thee cursor, and an additional addressing strip in.plate 42 would be required to selectively address the cursor cells.Although the cursor arrangement has been described in terms of rows ofcells beneath the sub-matrices, respectively, other indicatingarrangements of cells may be utilized to the same effect.

It is often a desideratum'with equipment of the character describedherein to provide means for indicating which of the display memory cells12 are lit. Such an indication is often required where the apparatus isutilized as a memory, and computer interrogation to determine the stateof the cells of the memory is desired.

Referring to FIG. la, a current sensor 95 is included and is selectivelyconnectible by conventional switching arrangements to the reservoirelectrode plates 13 and 15. In order to interrogate the status of aparticular memory cell 12 (FIG. addressing potentials are applied by thecircuit 83 (FIG. 1b) so as to extend a plasma column from the selectedmemory cell back to the reservoir 10 (FIG. la). If the selected memorycell 12 is lit such a plasma column will be generated, the resultingcurrent being detected by the current sensor 95.

If the selected display cell is not lit, a plasma column will not beextended and current will not be sensed.

Thus the status of the memory cells 12 may be determined by the currentsensor 95. It is appreciated that in this mode of operation the memorycells 12 provide the function of a plasma reservoir in the sensedescribed hereinabove for the reverse operation.

While the invention has been described in its preferred embodiment, itis to be understood that the words which have been used are words ofdescription rather than limitation and that changes within the purviewof the appended claims may be made without departing from the true scopeand spirit of the invention in its broader aspects. I

We claim:

1. Gas discharge display apparatus comprising reservoir means forcontaining an ioniz'able gas,

means in said reservoir means for partitioning said reservoir means intoat least partially isolated gas discharge reservoir cells at most weaklycoupled to each other,

a plurality of gas discharge display memory cell means, and

a plurality of addressing electrode means interposed between saidreservoir means and said display memory cell means and each having aplurality of apertures therethrough,

said plurality of addressing electrode means being in superposedarrangement with respect to each other with said apertures aligned toform a plurality of gas conductive channels extending, respectively,from said reservoir cells to said display memory cell means,

said plurality of addresssing electrode means being adapted forconnection to sources of selectible electrical potential for selectivelyapplying potentials to said addressing electrode means to selectivelyextend gas discharge columns in said channels from said reservoir meansto said display memory cell means for igniting gas displays in selecteddisplay memory cell means.

2. The apparatus of claim 1 in which each said reservoir cell includesreservoir means adapted for connection to a source of ionizing potentialfor ionizing said ionizable gas.

3. The apparatus of claim 2 in which said reservoir electrode meanscomprises reservoir anode means and reservoir cathode means.

4. The apparatus of claim 3 in which said partitioning means comprisesapertured 'plate means of electrically insulating material associatedwith said reservoir cathode means.

5. The apparatus of claim 1 in which said reservoir means includes meansfor at most weakly coupling said reservoir cells to each other.

6. The apparatus of claim 1 in which said reservoir means comprisesfirst reservoir electrode plate means having a plurality of aperturestherethrough coupled with said gas conductive channels, respectively,

first electrically insulating plate means adjacent said first reservoirelectrode plate means having a plurality of apertures therethrough,

second reservoir electrode plate means adjacent said first electricallyinsulating plate means having a spacer plate means adjacent said secondelectrically insulating plate means having openings therethrough eachbeing associated with pluralities of said apertures for providing saidweak coupling between said reservoir cells, and

cover plate means adjacent said spacer plate means,

the above mentioned plate means being in superposed arrangement withrespect to each other to form said reservoir means with said aperturesaligned whereby to form said reservoircells, respectively,

said first and second insulating plate means forming said partitioningmeans,

said first and second reservoir electrode .plate means being adapted forconnection to a source of ionizing potential for ionizing said gas insaid reservoir cells.

7. The apparatus of claim 6 in which said first reservoir electrodeplate means comprises substantially parallel first electricallyconductive strips electrically insulated from each other, and

said second reservoir electrode plate means comprises substantiallyparallel second electrically conductive strips electrically insulatedfrom each other and transverse to said first strips.

8. The apparatus of claim 7 in which the intersections of said first andsecond strips are associated with pluralities of said apertures.

9. The apparatus of claim 8" in which said first and second reservoirelectrode plate means comprise reservoir anode means and reservoircathode means, respectively, said strips being adapted for selectiveconnection to a source of ionizing potential for ionizing the gas in thereservoir cells at the intersections of the energized strips.

10. Gas discharge display apparatus for displaying symbols comprisingreservoir means for containing an ionizable gas,

a plurality of gas discharge display memory cell means arranged in rowsand columns,

' first addressingelectrode plate means interposed between saidreservoirmeans and said display memory cell means with a plurality ofapertures therethrough arranged in rows and columns and havingsubstantially parallel first electrically conductive addressing stripseach encompassing. a plurality of rows of said apertures to define theheight of said symbols,

second addressing electrode plate means interposed between saidreservoir means and said display memory cell means with a plurality ofapertures therethrough arranged in rows and columns and havingsubstantially parallel second electrically conductive addressingstripseach encompassing a plurality of columns of said apertures todefine the width of said symbols, and

third and fourth addressing electrode plate means interposed betweensaid reservoir means and said display memory cell means each with aplurality of apertures therethrough arranged in rows and columns andhaving third and fourth electrically con-.

ductive addressing strips, respectively, substantially parallel to saidfirst and second strips, respectively, for defining said symbols,

said first, second, third and fourth addressing electrode plate meansbeing in superposed arrangement with respect to each other with saidapertures aligned to form a plurality of gas conductive chan nelsextending from said reservoir means to said display memory cell means,respectively,

said first and second addressing electrode plate means being adapted forconnection to sources of selectible electrical potential for selectivelyapplying potentials thereto for selectively extending gas dischargecolumns in said channels from said reservoir means to define the heightand width of said symbols,

said third and fourth addressing electrode plate means being adapted forconnection to sources of selectible electrical potential for selectivelyapplying potentials thereto for selectively extending gas dischargecolumns in said channels from said reservoir means to said displaymemory cell means for igniting gas discharges in selected display memorycell means to form said symbols.

11. The apparatus of claim 10 in which said third electricallyconductive addressing strips encompass said rows of said apertures,respectively, and

said fourth electrically conductive addressing strips encompass saidcolumns of said apertures, respectively.

12. The apparatus of claim 11 in which at least one of said addressingelectrode plate means includes electrically conductive interconnectingstrips in substanbetween said reservoir means and said displaymemorycell means and each having a plurality of apertures therethrough,

said plurality of addressing electrode means being in superposedarrangement with respect to each other with said apertures aligned toform a plurality of gas conductive channels extending from saidreservoir means to said display memory cell means, respectively,

said plurality of addressing electrode means being adapted forconnection to sources of selectible electrical potential for selectivelyapplying potentials to said addressing electrode means to selectivelyextend gas discharge columns in said channels from said reservoir meansto said display means for igniting gas discharges in selected dis- .playmemory cell means,

said plurality of gas discharge display memory cell means comprisingfirst and second display memory electrode means one of which having twoportions electrically insulated from each other and adapted forconnection to sources of gas discharge sustaining potential,respectively,

said plurality of gas discharge display memory cell means being arrangedin a matrix of rows and columns comprising a plurality of sub-matricesfor displaying said symbols and a plurality of indicia cells associated,respectively, with said sub-matrices,

said sub-matrices and said indicia cells being arranged on said twoportions of said display memory electrode means, respectively, wherebysaid indicia cells may be ignited and extinguished independently of saidsymbols.

14. The apparatus of claim 13 in which said indicia cells associatedwith each said sub-matrix comprise a row of cells beneath saidsub-matrix.

15. Gas discharge display apparatus comprising reservoir means forcontaining an ionizable gas,

a plurality of gas discharge display memory cell means,

a plurality of addressing electrode means interposed between saidreservoir means and said display memory cell means and each having aplurality of apertures therethrough,

said plurality of addressing electrode means being in superposedarrangement with respect to each other with said apertures aligned toform a plurality of gas conductive channels extending from saidreservoir means to said display memory cell means, respectively,

said plurality of addressing electrode means being said plurality ofaddressing electrode means being further adapted forconnection tosources of selectible electrical potential for selectively applyingpotentials to said addressing electrode means to selectively extend gasdischarge columns in said channels from lit display memory cell means tosaid reservoir means, and

means coupled with said reservoir means for sensing current associatedwith said gas discharge columns extended from said lit display memorycell means tosaid reservoir means thereby providing indications of thelit cells.

1. Gas discharge display apparatus comprising reservoir means forcontaining an ionizable gas, means in said reservoir means forpartitioning said reservoir means into at least partially isolated gasdischarge reservoir cells at most weakly coupled to each other, aplurality of gas discharge display memory cell means, and a plurality ofaddressing electrode means interposed between said reservoir means andsaid display memory cell means and each having a plurality of aperturestherethrough, said plurality of addressing electrode means being insuperposed arrangement with respect to each other with said aperturesaligned to form a plurality of gas conductive channels extending,respectively, from said reservoir cells to said display memory cellmeans, said plurality of addresssing electrode means being adapted forconnection to sources of selectible electrical potential for selectivelyapplying potentials to said addressing electrode means to selectivelyextend gas discharge columns in said channels from said reservoir meansto said display memory cell means for igniting gas displays in selecteddisplay memory cell means.
 2. The apparatus of claim 1 in which eachsaid reservoir cell includes reservoir means adapted for connection to asource of ionizing potential for ionizing said ionizable gas.
 3. Theapparatus of claim 2 in which said reservoir electrode means comprisesreservoir anode means and reservoir cathode means.
 4. The apparatus ofclaim 3 in which said partitioning means comprises apertured plate meansof electrically insulating material associated with said reservoircathode means.
 5. The apparatus of claim 1 in which said reservoir meansincludes means for at most weakly coupling said reservoir cells to eachother.
 6. The apparatus of claim 1 in which said reservoir meanscomprises first reservoir electrode plate means having a plurality ofapertures therethrough coupled with said gas conductive channels,respectively, first electrically insulating plate means adjacent saidfirst reservoir electrode plate means having a plurality of aperturestherethrough, second reservoir electrode plate means adjacent said firstelectrically insulating plate means having a plurality of aperturestherethrough, second electrically insulating plate means adjacent saidsecond reservoir electrode plate means having a plurality of aperturestherethrough, spacer plate means adjacent said second electricallyinsulating plate means having openings therethrough each beingassociated with pluralities of said apertures for providing said weakcoupling between said reservoir cells, and cover plate means adjacentsaid spacer plate Means, the above mentioned plate means being insuperposed arrangement with respect to each other to form said reservoirmeans with said apertures aligned whereby to form said reservoir cells,respectively, said first and second insulating plate means forming saidpartitioning means, said first and second reservoir electrode platemeans being adapted for connection to a source of ionizing potential forionizing said gas in said reservoir cells.
 7. The apparatus of claim 6in which said first reservoir electrode plate means comprisessubstantially parallel first electrically conductive strips electricallyinsulated from each other, and said second reservoir electrode platemeans comprises substantially parallel second electrically conductivestrips electrically insulated from each other and transverse to saidfirst strips.
 8. The apparatus of claim 7 in which the intersections ofsaid first and second strips are associated with pluralities of saidapertures.
 9. The apparatus of claim 8 in which said first and secondreservoir electrode plate means comprise reservoir anode means andreservoir cathode means, respectively, said strips being adapted forselective connection to a source of ionizing potential for ionizing thegas in the reservoir cells at the intersections of the energized strips.10. Gas discharge display apparatus for displaying symbols comprisingreservoir means for containing an ionizable gas, a plurality of gasdischarge display memory cell means arranged in rows and columns, firstaddressing electrode plate means interposed between said reservoir meansand said display memory cell means with a plurality of aperturestherethrough arranged in rows and columns and having substantiallyparallel first electrically conductive addressing strips eachencompassing a plurality of rows of said apertures to define the heightof said symbols, second addressing electrode plate means interposedbetween said reservoir means and said display memory cell means with aplurality of apertures therethrough arranged in rows and columns andhaving substantially parallel second electrically conductive addressingstrips each encompassing a plurality of columns of said apertures todefine the width of said symbols, and third and fourth addressingelectrode plate means interposed between said reservoir means and saiddisplay memory cell means each with a plurality of aperturestherethrough arranged in rows and columns and having third and fourthelectrically conductive addressing strips, respectively, substantiallyparallel to said first and second strips, respectively, for definingsaid symbols, said first, second, third and fourth addressing electrodeplate means being in superposed arrangement with respect to each otherwith said apertures aligned to form a plurality of gas conductivechannels extending from said reservoir means to said display memory cellmeans, respectively, said first and second addressing electrode platemeans being adapted for connection to sources of selectible electricalpotential for selectively applying potentials thereto for selectivelyextending gas discharge columns in said channels from said reservoirmeans to define the height and width of said symbols, said third andfourth addressing electrode plate means being adapted for connection tosources of selectible electrical potential for selectively applyingpotentials thereto for selectively extending gas discharge columns insaid channels from said reservoir means to said display memory cellmeans for igniting gas discharges in selected display memory cell meansto form said symbols.
 11. The apparatus of claim 10 in which said thirdelectrically conductive addressing strips encompass said rows of saidapertures, respectively, and said fourth electrically conductiveaddressing strips encompass said columns of said apertures,respectively.
 12. The apparatus of claim 11 in which at least one ofsaid addressing electRode plate means includes electrically conductiveinterconnecting strips in substantially the same plane as saidaddressing strips for interconnecting said addressing strips to form apredetermined number of continuous non-overlapping strips disposed in ato-and-fro manner on said addressing electrode plate means.
 13. Gasdischarge display apparatus for displaying symbols comprising reservoirmeans for containing an ionizable gas, a plurality of gas dischargedisplay memory cell means, and a plurality of addressing electrode meansinterposed between said reservoir means and said display memory cellmeans and each having a plurality of apertures therethrough, saidplurality of addressing electrode means being in superposed arrangementwith respect to each other with said apertures aligned to form aplurality of gas conductive channels extending from said reservoir meansto said display memory cell means, respectively, said plurality ofaddressing electrode means being adapted for connection to sources ofselectible electrical potential for selectively applying potentials tosaid addressing electrode means to selectively extend gas dischargecolumns in said channels from said reservoir means to said display meansfor igniting gas discharges in selected display memory cell means, saidplurality of gas discharge display memory cell means comprising firstand second display memory electrode means one of which having twoportions electrically insulated from each other and adapted forconnection to sources of gas discharge sustaining potential,respectively, said plurality of gas discharge display memory cell meansbeing arranged in a matrix of rows and columns comprising a plurality ofsub-matrices for displaying said symbols and a plurality of indiciacells associated, respectively, with said sub-matrices, saidsub-matrices and said indicia cells being arranged on said two portionsof said display memory electrode means, respectively, whereby saidindicia cells may be ignited and extinguished independently of saidsymbols.
 14. The apparatus of claim 13 in which said indicia cellsassociated with each said sub-matrix comprise a row of cells beneathsaid sub-matrix.
 15. Gas discharge display apparatus comprisingreservoir means for containing an ionizable gas, a plurality of gasdischarge display memory cell means, a plurality of addressing electrodemeans interposed between said reservoir means and said display memorycell means and each having a plurality of apertures therethrough, saidplurality of addressing electrode means being in superposed arrangementwith respect to each other with said apertures aligned to form aplurality of gas conductive channels extending from said reservoir meansto said display memory cell means, respectively, said plurality ofaddressing electrode means being adapted for connection to sources ofselectible electrical potential for selectively applying potentials tosaid addressing electrode means to selectively extend gas dischargecolumns in said channels from said reservoir means to said displaymemory cell means for igniting gas discharges in selected display memorycell means, said plurality of addressing electrode means being furtheradapted for connection to sources of selectible electrical potential forselectively applying potentials to said addressing electrode means toselectively extend gas discharge columns in said channels from litdisplay memory cell means to said reservoir means, and means coupledwith said reservoir means for sensing current associated with said gasdischarge columns extended from said lit display memory cell means tosaid reservoir means thereby providing indications of the lit cells.